CN105264341B - Thermal flowmeter, temperature measuring device, and thermal flow rate calculating method - Google Patents

Thermal flowmeter, temperature measuring device, and thermal flow rate calculating method Download PDF

Info

Publication number
CN105264341B
CN105264341B CN201480031064.6A CN201480031064A CN105264341B CN 105264341 B CN105264341 B CN 105264341B CN 201480031064 A CN201480031064 A CN 201480031064A CN 105264341 B CN105264341 B CN 105264341B
Authority
CN
China
Prior art keywords
fluid
correction
temperature
voltage
upstream
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN201480031064.6A
Other languages
Chinese (zh)
Other versions
CN105264341A (en
Inventor
白井隆
冈野浩之
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Horiba Stec Co Ltd
Original Assignee
Horiba Stec Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Horiba Stec Co Ltd filed Critical Horiba Stec Co Ltd
Publication of CN105264341A publication Critical patent/CN105264341A/en
Application granted granted Critical
Publication of CN105264341B publication Critical patent/CN105264341B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
    • G01F1/696—Circuits therefor, e.g. constant-current flow meters
    • G01F1/6965—Circuits therefor, e.g. constant-current flow meters comprising means to store calibration data for flow signal calculation or correction
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
    • G01F1/684—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
    • G01F1/684—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
    • G01F1/688—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow using a particular type of heating, cooling or sensing element
    • G01F1/69—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow using a particular type of heating, cooling or sensing element of resistive type
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
    • G01F1/696—Circuits therefor, e.g. constant-current flow meters
    • G01F1/698—Feedback or rebalancing circuits, e.g. self heated constant temperature flowmeters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K13/00—Thermometers specially adapted for specific purposes
    • G01K13/02—Thermometers specially adapted for specific purposes for measuring temperature of moving fluids or granular materials capable of flow
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
    • G01K7/16—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Measuring Volume Flow (AREA)
  • Details Of Flowmeters (AREA)

Abstract

The present invention provides a thermal flowmeter capable of correcting a zero point error and a span error that change in accordance with an ambient temperature more accurately than in the past, and capable of reducing time and labor for specifying by simply calculating a correction amount for correction by a general-purpose calculation formula regardless of a fluid type, the thermal flowmeter including: a flow passage through which a fluid of a measurement object flows; an upstream resistance element disposed upstream of the flow channel; a downstream resistance element disposed downstream of the flow channel; a flow rate calculation unit that calculates a flow rate of the fluid to be measured based on an upstream voltage that is a voltage applied to the upstream resistance element, a downstream voltage that is a voltage applied to the downstream resistance element, and a thermal conductivity of the fluid to be measured.

Description

Thermal flowmeter, temperature measuring device, and thermal flow rate calculating method
Technical Field
The present invention relates to a thermal flow meter and a program for the thermal flow meter, in which two resistance elements are provided in a flow path through which a fluid to be measured flows, and the flow rate of the fluid to be measured is measured based on a voltage applied to cause the resistance elements to generate heat.
Background
For example, a thermal flowmeter of a constant temperature drive system controls applied voltages so that the temperatures of resistance elements provided upstream and downstream of a flow channel are constant, and calculates the flow rate of a fluid flowing through the flow channel based on the upstream voltage and the downstream voltage at that time. More specifically, as shown in equation 1, the flow rate is determined from the sensor output obtained by dividing the voltage difference, which is the difference between the upstream voltage and the downstream voltage, by the sum of the upstream voltage and the downstream voltage.
[ mathematical formula 1]
Q＝Sens((Vu-Vd)/(Vu+Vd)) (1)
Wherein, Q: flow, Sens: evaluation constant (value け constant), Vu: upstream voltage, Vd: downstream voltage, (Vu-Vd)/(Vu + Vd): and (6) outputting by a sensor.
To qualitatively explain equation 1, Vu-Vd is a value that changes depending on the flow rate and temperature of the fluid flowing through the flow channel, and Vu + Vd is a value that changes substantially depending on the temperature, so it is considered that (Vu-Vd)/(Vu + Vd) ideally changes depending only on the flow rate of the fluid.
However, in practice, the flow rate calculated by equation 1 has a zero point error and a span error due to the influence of the type of fluid to be measured, the ambient temperature, the temperature of the fluid, and the like.
For example, even in a state where the fluid is not flowing, if the ambient temperature changes, the zero point output of Vu-Vd changes, and the flow rate Q calculated by equation 1 cannot become zero.
Therefore, as shown in patent document 1 and the like, a zero point correction function M including Vu + Vd is defined as a temperature index, and zero point correction is performed by making a value of ((Vu-Vd)/(Vu + Vd)) -M when no fluid flows zero regardless of the ambient temperature.
However, since the temperature index Vu + Vd used as a variable of the zero point correction function M has a linear characteristic only for a part of the temperature range, even if the zero point correction method of patent document 1 is used, the zero point correction can be sufficiently performed only in the range of 15 to 35 ℃.
Further, since the zero point correction function M is affected by the kind of fluid, the zero point correction function M differs for each fluid. Therefore, it is necessary to determine the zero point correction function M in advance for each fluid to be measured, which is very troublesome in actual measurement. In other words, since the relationship between the zero point correction function M and the type of fluid has not been completely clarified in the past, if the work of specifying the zero point correction function M or the like is not accurately performed for each type, correction cannot be performed with high accuracy.
This problem similarly occurs when the span correction of the flow rate calculated by equation 1 or the like is performed.
Documents of the prior art
Patent document
Patent document 1: japanese patent laid-open No. JP-B-O2875919
Disclosure of Invention
Technical problem to be solved by the invention
The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a thermal flowmeter and a program for a thermal flowmeter, which can correct a zero point error and a span error according to a change in an environmental temperature more accurately than ever, and can easily calculate a correction amount for correction using a general-purpose calculation formula regardless of a fluid type, thereby reducing time and labor for specifying the correction amount.
Technical scheme for solving technical problem
That is, the present invention provides a thermal type flow meter including: a flow passage through which a fluid of a measurement object flows; an upstream resistance element disposed upstream of the flow channel; a downstream resistance element disposed downstream of the flow channel; and a flow rate calculation unit that calculates an ambient temperature based on an upstream voltage, which is a voltage applied to the upstream resistive element, a downstream voltage, which is a voltage applied to the downstream resistive element, and a thermal conductivity of the fluid to be measured, and calculates a flow rate of the fluid to be measured based on the upstream voltage, the downstream voltage, and the ambient temperature, the flow rate calculation unit calculating a temperature index before correction from a sum of the upstream voltage and the downstream voltage; calculating a correction constant from the thermal conductivity of the fluid of the measurement object; calculating a corrected temperature index according to the temperature index before correction and the correction constant; calculating the environmental temperature according to the corrected temperature index; and calculating the flow rate of the fluid of the measuring object according to the difference between the upstream voltage and the downstream voltage and the environment temperature.
Further, as a result of intensive studies by the inventors of the present invention, it was found for the first time that: the present invention was made in view of the fact that the zero point error and the span error of the thermal flowmeter have a close relationship with the thermal conductivity of the measurement target, and the accuracy of the output flow rate can be improved compared to the conventional one by using the thermal conductivity as a parameter.
In this way, since the thermal conductivity of the fluid having a close relationship with the zero point error and the span error is used for the output of the flow rate, the output flow rate can be set to a value closer to the actual flow rate than in the related art.
Further, by using the thermal conductivity, even if the fluid type is different, a correction amount corresponding to a zero point error and a span error that change due to a change in the environmental temperature or the like can be calculated by a common calculation formula. Therefore, the time and labor for determining the correction amount in advance for reducing the zero point error and the span error can be reduced as compared with the conventional art.
In order to realize zero point correction with good accuracy by using thermal conductivity, it is preferable that the flow rate calculation unit includes: a sensor output calculation unit that calculates a sensor output related to the flow rate of the fluid to be measured based on a voltage difference that is a difference between the upstream voltage and the downstream voltage; a zero point correction amount calculation unit that calculates a zero point correction amount of the sensor output based on a thermal conductivity of the fluid to be measured; and a correction calculation unit that calculates a corrected flow rate based on at least the sensor output and the zero point correction amount.
As a specific configuration for making the flow rate output from the thermal type flow meter zero when the fluid stops even if the ambient temperature changes in a wide temperature range, there can be mentioned: the zero point correction amount calculation unit includes: a zero point correction temperature function storage section that stores a zero point correction temperature function as a function of temperature, the zero point correction temperature function being determined as: a difference between the fluid to be measured and the sensor output becomes zero in a predetermined temperature range when the fluid does not flow in the flow channel; a corrected temperature index calculation unit that calculates a corrected temperature index based on at least a temperature index before correction calculated from the upstream voltage and the downstream voltage and a correction constant calculated from a thermal conductivity of the fluid to be measured; a current temperature calculation unit for calculating a current temperature based on the corrected temperature index; and a zero point correction amount determination unit that determines a zero point correction amount based on the zero point correction temperature function and the current temperature. In this way, since the post-correction temperature index that changes substantially in proportion to the change in the ambient temperature can be calculated using the correction constant calculated from the thermal conductivity, the zero point correction amount of the current state can be obtained from the zero point correction temperature function in a state where the ambient temperature is accurately grasped. Therefore, even if a thermometer is not provided, the zero point correction can be accurately performed only on the basis of the data obtained by the thermal flowmeter, and the accuracy of the output flow rate can be improved.
In order to obtain the correction constant from the calculation formula regardless of the type of fluid as long as the thermal conductivity is known and to eliminate the need for an experiment for determining the correction constant, for example, each time the type of fluid is changed, it is preferable that the correction constant is a value calculated based on the square of the inverse of the thermal conductivity.
In order to obtain the correction amount in the current state from the zero point correction amount temperature function in a wide temperature range in a case where the ambient temperature changes, while making the pre-correction temperature index show good linear characteristics, it is preferable that the pre-correction temperature index is a sum of a square of the upstream voltage and the downstream voltage or a sum of a square of the upstream voltage and a square of the downstream voltage.
In order to obtain a zero point correction amount that more closely matches the current state by reflecting the influence of the actually flowing flow rate as well as the ambient temperature by the correction constant, it is preferable that the post-correction temperature index calculation unit calculates the post-correction temperature index based on the pre-correction temperature index, the correction constant, and a sensor output.
In order to output a flow rate with zero point error correction substantially always regardless of the ambient temperature, the actual flow rate, the fluid type, and the like, it is preferable that the flow rate output unit outputs the flow rate of the fluid to be measured based on the following equation 2.
[ mathematical formula 2]
Wherein, t: temperature, G (t): temperature function of flow, Vu: upstream voltage, Vd: downstream voltage, (Vu-Vd)/(Vu + Vd): sensor output, f (t): zero point correction temperature function, a, b, c, d: coefficients of the zero point correction temperature function, Y: corrected temperature index, e, f: the slope and intercept when the corrected temperature index is expressed as a temperature linear equation (Vu + Vd)2: temperature index before correction, K: correction constant, SET: the proportion of the sensor output relative to full scale.
In order to be able to correct the span error that changes in response to a change in the ambient temperature with high accuracy, the flow rate calculation unit further includes a span correction amount calculation unit that calculates a span correction amount of the sensor output based on the thermal conductivity of the fluid to be measured, and the correction calculation unit calculates the corrected flow rate based on at least the sensor output and the span correction amount.
In order to improve the accuracy of the flow rate by accurately correcting both a component due to a change in the ambient temperature and a component due to the characteristic of the fluid to be measured in the span error, it is preferable that the span correction amount includes: a universal range correction component that changes only depending on temperature; and a fluid-inherent range correction component that changes depending on at least the thermal conductivity of the fluid to be measured.
In order to enable the span correction corresponding to each fluid of the measurement object to be performed with high accuracy, it is preferable that the fluid-inherent span correction component be defined as a function having the thermal conductivity, the sensor output, and the temperature as variables.
In order to correct the influence of the structure of the flow channel through which the fluid to be measured flows, or the like, on the flow rate, it is preferable that the flow channel includes: a bypass flow passage through which the fluid of the measurement object flows, the bypass flow passage being provided with a fluid resistance element; and a sensor flow path provided so as to connect the fluid resistance element to the bypass flow path in the front-rear direction, the upstream resistance element and the downstream resistance element being provided on the outer side, the span correction amount further including a bypass span correction component for performing correction corresponding to the bypass flow path, the bypass span correction component being a function having at least the thermal conductivity of the fluid to be measured as a variable.
As a specific expression for correcting the span error that varies depending on the environmental temperature, the actual flow rate, and the type of fluid with high accuracy, it is preferable that the flow rate output unit outputs the flow rate of the fluid to be measured based on the following expression 3.
[ mathematical formula 3]
Wherein, t: temperature, G (t): temperature function of flow, Vu: upstream voltage, Vd: downstream voltage, (Vu-Vd)/(Vu + Vd): sensor output, f (t): zero point correction temperature function, a, b, c, d: coefficients of the zero point correction temperature function, Y: corrected temperature index, e, f: the slope and intercept when the corrected temperature index is expressed as a temperature linear equation (Vu + Vd)2: temperature index before correction, K: correction constant, SET: proportion of sensor output to full scale (proportion of flow rate value before correction to full scale), S: span correction amount, h (t): function representing the universal range correction component, i (t, λ, SET): function representing fluid inherent range correction component, j (λ, t): a function representing a bypass range correction component.
In order to be able to calculate the current temperature of the fluid from the upstream voltage and the downstream voltage and improve the accuracy of the current temperature calculated by the thermal conductivity of the fluid of the measurement object, the present invention also provides a temperature measuring apparatus comprising: a flow passage through which a fluid of a measurement object flows; an upstream resistance element disposed upstream of the flow channel; a downstream resistance element disposed downstream of the flow channel; a post-correction temperature index calculation unit that calculates a post-correction temperature index based on at least a pre-correction temperature index calculated from an upstream voltage that is a voltage applied to the upstream resistance element and a downstream voltage that is a voltage applied to the downstream resistance element, and a correction constant calculated from a thermal conductivity of the fluid to be measured; and a current temperature calculation unit for calculating a current temperature based on the corrected temperature index.
In order to update a program for calculating a flow rate in a conventional thermal flow meter and output a flow rate with a zero point error and a span error reduced more than those in the conventional art, the present invention also provides a program for a thermal flow meter, the thermal flow meter including: a flow passage through which a fluid of a measurement object flows; an upstream resistance element disposed upstream of the flow channel; and a downstream resistance element provided downstream of the flow path, wherein the thermal flow meter program causes a computer to function as a flow rate calculation unit that calculates a flow rate of the fluid to be measured based on an upstream voltage applied to the upstream resistance element, a downstream voltage applied to the downstream resistance element, and a thermal conductivity of the fluid to be measured. For example, when the program is updated, a program medium for a thermal flowmeter in which the program for a thermal flowmeter is stored in a recording medium such as a CD, DVD, or flash memory can be used.
Effects of the invention
Thus, according to the thermal flow meter of the present invention, since the flow rate is output based on the upstream voltage, the downstream voltage, and the thermal conductivity of the measurement target, the zero point error and the span error having a relationship with the thermal conductivity can be corrected with high accuracy, and a value close to the actual flow rate can be output. Further, since the correction amount corresponding to the type of the fluid to be measured can be calculated based on the thermal conductivity, a predetermined calculation formula, and the like, it is possible to omit a part of experiments and the like for specifying parameters necessary for generating the correction amount.
Drawings
Fig. 1 is a schematic diagram showing a sensor portion of a thermal type flow meter according to an embodiment of the present invention.
Fig. 2 is a functional block diagram showing a calculation means of a thermal flowmeter according to the same embodiment as that of fig. 1.
Fig. 3 is a diagram of measured data showing a relationship between a temperature index before correction and an ambient temperature.
Fig. 4 is a graph showing the influence of the flow rate on the relationship between the temperature index before correction and the ambient temperature for each fluid, and a graph showing the relationship between the change rate and the thermal conductivity obtained from the graphs.
Fig. 5 is a graph showing the influence of the relationship between the change rate of the flow rate and the flow rate for each fluid, and a graph showing the relationship between the change rate and the thermal conductivity obtained from each graph.
Fig. 6 is a diagram showing the result of correction of the zero point correction amount according to the present embodiment.
Fig. 7 is a diagram showing a span error occurring in the conventional thermal flowmeter.
Fig. 8 is a graph showing the slope of the fluid intrinsic span error with respect to the flow rate and the relationship between the slope and the thermal conductivity calculated from the graph.
Fig. 9 is a diagram showing the range correction result by only the general range correction component and the fluid specific range correction component.
Fig. 10 is a diagram showing the result of span correction by the span correction amount including all the components.
Description of the reference numerals
100 thermal flowmeter
1 u.upstream constant temperature control circuit
1 d.downstream constant temperature control circuit
2. flow rate calculating section
3. sensor output calculating section
4 zero point correction amount calculating section
41 zero point correction temperature function storage part
42 DEG corrected temperature index calculating part
43. Current temperature calculating section
44 DEG zero correction amount determining part
5 DEG
51 DEG
52 DEG
6 correction calculation section
Detailed Description
The thermal flow meter 100 according to the present embodiment will be described below with reference to the drawings.
The thermal flowmeter according to the present embodiment is used for non-contact measurement of the flow rate of a gas used in, for example, a semiconductor manufacturing process. Here, the gas used is a corrosive gas (BCl)2、Cl2、HCl、ClF3Etc.), reactive gas (SiH)4、B2H6Etc.) and inert gas (N)2He, etc.) and the like.
More specifically, as shown in the schematic diagram of fig. 1, the thermal flow meter 100 includes: a bypass flow path BC through which a gas as a fluid flows; a sensor flow path SC through which the gas branched from the bypass flow path BC flows in the narrow tube branched from the bypass flow path BC; flow measurement means FM for measuring a flow rate based on the gas flowing through the sensor flow passage SC; and a laminar flow element FR as a fluid resistance, provided between a branching point and a merging point of the branching flow path of the bypass flow path BC, and having a plurality of internal flow paths. The laminar flow element FR has a flow dividing ratio between the bypass flow channel BC and the sensor flow channel SC set to a predetermined design value, and may be formed by inserting a plurality of narrow tubes into an outer tube or by stacking a plurality of thin flat plates having a plurality of through holes.
The sensor flow path SC is formed of a substantially U-shaped hollow thin tube made of metal such as stainless steel. Two resistance elements provided in the flow rate measurement mechanism FM are wound around a linear portion of the narrow tube corresponding to the U-shaped bottom portion.
The flow rate measurement mechanism FM includes: a sensor unit SP that outputs a signal corresponding to the flow rate of the gas flowing through the sensor flow path SC; and a flow rate calculation unit 2 that calculates the mass flow rate of the gas flowing through the sensor flow path SC and the bypass flow path BC based on the output from the sensor unit SP.
The sensor section SP includes: an upstream resistive element Ru as a coil wound on the outer surface of the fine tube upstream of the sensor flow channel SC; and a downstream resistance element Rd as a coil wound on the outer surface of the tubule downstream of the sensor flow channel SC. The upstream resistance element Ru and the downstream resistance element Rd are formed of heating resistance wires whose resistance values increase and decrease with a change in temperature, and serve as a heating device and a temperature detection device in one member.
The sensor unit SP is of a constant temperature system, and the upstream constant temperature control circuit 1u is constituted by a bridge circuit including the upstream resistance element Ru as a part thereof, and the downstream constant temperature control circuit 1d is constituted by a bridge circuit including the downstream resistance element Rd as a part thereof.
The upstream constant temperature control circuit 1u includes: an upstream bridge circuit in which a series resistor group including the upstream resistor element Ru and a temperature setting resistor R1 connected in series with the upstream resistor element Ru and a series resistor group including two fixed resistors R2 and R3 connected in series are connected in parallel; and a feedback control circuit including an operational amplifier that feeds back a difference (Vu) between a potential of a connection point between the upstream resistance element Ru and the temperature setting resistor R1 and a potential of a connection point between the two fixed resistors to the upstream bridge circuit to maintain a balance of the upstream bridge circuit.
The downstream constant temperature control circuit 1d includes, as with the upstream constant temperature control circuit 1 u: a downstream bridge circuit in which a series resistor group including the downstream resistor element Rd and a temperature setting resistor R1 connected in series with the downstream resistor element Rd and a series resistor group including two fixed resistors R2 and R3 connected in series are connected in parallel; and a feedback control circuit including an operational amplifier that feeds back a difference (Vd) between a potential at a connection point between the downstream resistance element Rd and the temperature setting resistor R1 and a potential at a connection point between the two fixed resistors to the downstream bridge circuit so as to maintain a balance between the downstream bridge circuit.
Here, the upstream resistance element Ru and the downstream resistance element Rd are thermistors and are formed using materials having the same temperature coefficient of resistance. Further, the upstream resistance element Ru and the downstream resistance element Rd are feedback-controlled by the respective feedback control circuits so as to have the same resistance value as the temperature setting resistor R1. That is, since the resistance value is kept constant, the voltages Vu and Vd are controlled so that the temperatures of the upstream resistance element Ru and the downstream resistance element Rd are also kept constant. In the present embodiment, Vu and Vd are used as an upstream voltage Vu and a downstream voltage Vd, respectively, which are applied to cause the upstream resistance element Ru and the downstream resistance element Rd to generate heat.
The flow rate calculation unit 2 calculates the flow rate of the gas to be measured flowing through the sensor flow path SC and the bypass flow path BC based on values of an upstream voltage Vu applied to cause the upstream resistance element Ru to generate heat, a downstream voltage Vd applied to cause the downstream resistance element Rd to generate heat, and the thermal conductivity of the fluid to be measured.
The flow rate calculating unit 2 is configured to execute a program for the thermal flow meter 100 stored in a memory by a computer having a memory, a CPU, an input/output device, an a/D converter, a D/a converter, and the like. More specifically, the flow rate calculating unit 2 calculates the flow rate based on the following equation 4.
[ mathematical formula 4]
Here, t: temperature, G (t): temperature function of flow, Vu: upstream voltage, Vd: downstream voltage, (Vu-Vd)/(Vu + Vd): sensor output, f (t): zero point correction temperature function, a, b, c, d: coefficients of the zero point correction temperature function, Y: corrected temperature index, e, f: the corrected temperature index is expressed asSlope and intercept at first order of temperature, (Vu + Vd)2: temperature index before correction, K: correction constant, λ: thermal conductivity of the fluid of the measurement object, SET: proportion of sensor output to full scale (proportion of flow rate value before correction to full scale), S: span correction amount, h (t): function representing the universal range correction component, i (t, λ, SET): function representing fluid inherent range correction component, j (λ, t): a function representing a bypass range correction component.
In order to perform the calculation by the above equation 4, as shown in the functional block diagram of fig. 2, the flow rate calculating unit 2 at least realizes the functions of the sensor output calculating unit 3, the zero point correction amount calculating unit 4, the span correction amount calculating unit 5, and the correction calculating unit 6.
Each part will be explained.
The sensor output calculation unit 3 calculates a sensor output related to the fluid flow rate to be measured based on a voltage difference that is a difference between the upstream voltage Vu and the downstream voltage Vd. More specifically, the sensor output Vc is calculated based on the following equation 5.
[ math figure 5]
The zero point correction amount calculation unit 4 calculates a zero point correction amount of the sensor output based on the thermal conductivity of the fluid to be measured, and calculates the zero point correction amount by solving the following equations 6, 7, and 8.
[ mathematical formula 6]
F(t)＝at3+bt2+ct+d (6)
[ math figure 7]
t＝(Y-f)/e (7)
[ mathematical formula 8]
Y＝(Vu+Vd)2/(1+K(K-1)*SET2) (8)
That is, as shown in mathematical expression 6, the zero point correction amount is expressed as a cubic expression having the ambient temperature as a variable. Further, the corrected temperature index calculated from the upstream voltage Vu and the downstream voltage Vd by equation 8 is converted into the ambient temperature by equation 7, and the ambient temperature is substituted into equation 6, whereby the zero point correction amount for each ambient temperature can be obtained.
Next, the zero point correction amount calculation unit 4 will be described in detail.
The zero point correction amount calculation unit 4 includes a zero point correction temperature function storage unit 41, a corrected temperature index calculation unit 42, a current temperature calculation unit 43, and a zero point correction amount determination unit 44.
The zero point correction temperature function storage unit 41 stores a zero point correction temperature function as a function of temperature, as shown in equation 6, which is determined as: when the fluid to be measured does not flow in the flow channel, the difference between the sensor output and the fluid in a predetermined temperature range, for example, 15 to 60 ℃ is always zero. More specifically, the zero point correction temperature function storage unit 41 stores coefficients a, b, c, and d of the cubic expression of equation 6. The coefficients of equation 6 are determined based on experiments so that the values always become equal to the sensor output when the fluid changes within the predetermined temperature range without flowing through the flow channel.
The post-correction temperature index calculation unit 42 calculates a post-correction temperature index based on a pre-correction temperature index calculated from the upstream voltage Vu and the downstream voltage Vd, a correction constant K calculated from the thermal conductivity of the fluid to be measured, and the current sensor output. In the present embodiment, as shown in equation 8, the square of the sum of the upstream voltage Vu and the downstream voltage Vd is used as the pre-correction temperature index. The linear characteristic of the pre-correction temperature index with respect to temperature is better than the sum of the upstream voltage Vu and the downstream voltage Vd which are used in the related art, and as shown in the measured data in fig. 3, a calibration curve showing the relationship between the pre-correction temperature index and the ambient temperature can be expressed by a linear expression at least when the ambient temperature is in a temperature range of 15 to 60 ℃.
However, as shown in fig. 4, if the kind of fluid or the current flow rate flowing in the flow passage changes, the slope and intercept of the calibration curve change. That is, even if Y of equation 7 is substituted into the pre-correction temperature index, it is possible to calculate a temperature that deviates from the current ambient temperature. Therefore, by correcting the pre-correction temperature index in the post-correction temperature index calculation unit 42 as shown in equation 8, it is possible to calculate a temperature accurately reflecting the current ambient temperature regardless of the type of the fluid and the flow rate of the fluid.
First, the influence of the difference in the type of fluid on the calibration curve of the pre-correction temperature index and the ambient temperature will be described.
If the slope a of the calibration curve for the no-flow state (0% FS) of the fluid is compared for each gas type, respectively1Intercept b1And the slope a of the calibration curve for the full scale flow regime (100% FS)2Intercept b2The results are shown in table 1 below. Here, Ka、KbThe change rates at which the slope and intercept are multiplied by several times are expressed based on the state where the fluid is not flowing. Further, (a) of fig. 4 and (b) of fig. 4 show N listed in table 12And SF6Calibration curves of the pre-correction temperature index and the ambient temperature measured in each of the states of 0% FS and 100 FS. From the measurement results shown in fig. 4 (a) and 4 (b), an approximate straight line was created, and the slope and intercept of each fluid in table 1 were obtained.
[ Table 1]
Kind of fluid Slope a1 Slope ofa2 Variation ratio Ka Intercept b1 Intercept b2 Variation ratio Kb
N2 -3.624 -3.697 1.020 321.170 329.100 1.025
He -3.567 -3.570 1.001 319.130 319.970 1.003
Ar -3.592 -3.729 1.038 319.260 332.740 1.042
SF6 -3.604 -3.792 1.052 337.930 337.930 1.057
As can be seen from Table 1, the change ratio K of the slopeaAnd the ratio of change of intercept KbThe change ratio K of the slope may be substantially the same valueaAnd the ratio of change of intercept KbAnd is not expressed differently as the variation ratio K. The value of the change ratio K differs depending on the type of each fluid, but the inventors of the present invention have intensively studied and found that the change ratio K is a value that can be calculated from the thermal conductivity of the fluid. More specifically, as shown in the graph of fig. 4 (c), the change ratio K is a linear expression having the square of the inverse of the thermal conductivity as a variable, and the change ratio K of 100% FS of an arbitrary fluid can be calculated from the thermal conductivity by previously determining the slope and intercept of the calibration curve shown in the graph of fig. 4 (c).
However, the change ratio K varies depending on the flow rate of the fluid flowing through the flow channel even for the same fluid type. The inventors of the present invention conducted intensive studies on the results of measuring the relationship between the flow rate and the change ratio K shown in fig. 5 (a) and (b), and found for the first time that the change ratio K can be expressed by a linear expression when the square of the flow rate is used as a variable. Further, the coefficients of the linear expressions differ for each gas, and if SET, which is the ratio of the sensor output to the full scale, is used, it is as shown in table 2.
[ Table 2]
Here, since the change ratio K is based on a state where the fluid is not flowing, it is necessary to SET K to 1 when SET is zero. Therefore, each intercept in table 2 can be considered to be 1. In addition, if attention is paid to as (SET)2Change of coefficient ofThe slope of the ratio K, it can be seen that the ratio K varies from that of Table 1a、KbThe values after subtracting 1 are substantially equal. Therefore, the coefficients can be expressed as (K-1) using the change ratio K of 100% FS. As shown in the graph of fig. 5 (c), when the square of the reciprocal of the thermal conductivity of each fluid is used as a variable, the slope of the change ratio K may be expressed as a linear expression. Therefore, if the thermal conductivity is known, the slope of the change ratio K with respect to the square of the flow rate is also a value that can be calculated.
Thus, the influence of the type of fluid and the influence of the flow rate on the calibration curves of the temperature index before correction and the ambient temperature can be expressed by the change ratio K calculated from the thermal conductivity of the fluid, respectively. Therefore, the post-correction temperature index calculation unit 42 corrects the fluid type and the flow rate with respect to the pre-correction temperature index by using the change ratio K as the correction constant K.
More specifically, the post-correction temperature index calculation section 42 uses the pre-correction temperature index (Vu + Vd)2Dividing by a correction constant K, correcting the influence of different kinds of fluids, and using the pre-correction temperature index (Vu + Vd)2Divide by (K-1) SET2+1, the influence due to the flow rate is corrected.
The current temperature calculation unit 43 calculates the current temperature from the corrected temperature index by using equation 7. Here, the coefficients f and e for equation 7 are determined in advance by performing actual measurement or the like. The coefficients a, b, c, d, e, and f are predetermined based on measurement data obtained when a reference fluid type is caused to flow, and are not determined for each fluid. When the kind of the fluid is changed, an accurate ambient temperature can be obtained by changing according to the thermal conductivity of the fluid and using the correction constant K for calculating the corrected temperature index.
Table 3 shows a comparative example in which the value when the ambient temperature is calculated by equation 7 using the pre-correction temperature index and the value when the ambient temperature is calculated by equation 7 using the post-correction temperature index calculated by the post-correction temperature index calculation unit 42.
[ Table 3]
The flowing fluid being N220% FS case
The flowing fluid being N260% FS
The flowing fluid being SF620% FS case
The flowing fluid being SF660% FS
As can be seen from table 3, by using the corrected temperature index, the ambient temperature more accurate than the conventional one can be calculated regardless of the type and flow rate of the fluid.
The zero-point correction amount determination unit 44 determines a zero-point correction amount based on the zero-point correction temperature function and the current temperature. That is, the zero point correction amount determination unit 44 substitutes the ambient temperature obtained by expression 7 and expression 8 into the zero point correction temperature function of expression 6 to calculate the zero point correction amount, and transmits the value to the correction calculation unit 6. Fig. 6 is a graph showing the correction result of the zero point correction amount according to the present embodiment. In a state where the fluid is not flowing, the output of any fluid type can be made substantially zero in a range of 15 to 60 ℃, and a favorable zero point correction can be performed.
Next, the span correction amount calculation unit 5 that calculates the span correction amount of the sensor output will be described.
The span correction amount calculation unit 5 calculates a span correction amount of the sensor output based on the thermal conductivity of the fluid to be measured, using the ambient temperature calculated by the current temperature calculation unit 43.
More specifically, the span correction amount calculation unit 5 includes: a range correction function storage unit 51 for storing a range correction function represented by the following equation 9; and a span correction amount determination unit 52 that determines a span correction amount by substituting the current temperature obtained from the current temperature calculation unit 43, the sensor output, and the thermal conductivity of the fluid to be measured into the span correction function.
[ mathematical formula 9]
S＝h(t)+i(λ，t，SET)+j(λ，t) (9)
Wherein, S: span correction amount, h (t): function representing the universal range correction component, i (λ, t, SET): function representing fluid inherent range correction component, j (λ, t): a function representing a bypass range correction component. Further, h (t), i (λ, t, SET) are functions for correcting a span error due to the structure of the thermal flowmeter itself, and j (λ, t) is a function for correcting a span error due to the flow channel.
The reason why the span correction amount is defined by the three functions will be described. Fig. 7 is a graph showing a span error of each temperature with reference to a flow rate measured at 25 ℃ when the flow rate is measured by the conventional thermal flowmeter 100. In addition, the fluid species is SF6And He, which is a standard flowmeter that is not easily affected by temperature, is separately provided from the conventional thermal flowmeter. The span error shown in the graph indicates the amount by which the value shown in the conventional thermal flowmeter deviates from the value shown in the reference flowmeter.
Comparing fig. 7 (a) and (b), the span error is considered to include: a universal range error, which is generated in a manner of being substantially shifted depending on only the ambient temperature, regardless of the type and flow rate of the fluid; and a fluid-specific span error that varies in a rate of change with respect to the flow rate for each fluid and increases as the flow rate increases.
Therefore, the span correction amount includes at least a universal span component for correcting the universal span error and a fluid inherent span correction component for correcting the fluid inherent span error.
Here, when (b) of fig. 7 is observed, the He span error always has a substantially flat shape regardless of the flow rate at any temperature, only the general span error is remarkably shown, and the span error becomes large in association with a temperature 25 ℃. Therefore, a linear function of the temperature is generated from the relationship between the He temperature and the span error magnitude, and a function h (t) of the universal span correction component is determined as shown in the following equation 10.
[ mathematical formula 10]
h(t)＝C1t+C2 (10)
Wherein, C1、C2Is a constant determined based on the span error of He.
Next, the fluid intrinsic range correction component will be described.
As can be seen from the graph of span error against temperature change at 100% flow rate of fig. 8 (a), the slope of the span error inherent to the fluid for each fluid type against the ambient temperature is different for each fluid. As a result of intensive studies, the inventors of the present invention have found that, as shown in fig. 8 (b), the inclination of each straight line can be expressed by a linear expression having the reciprocal of the thermal conductivity of each fluid as a variable. Therefore, the function of the fluid intrinsic range correction component is defined as a function i (λ, t, SET) having temperature, thermal conductivity, and flow rate as variables.
More specifically, the function i (λ, t, SET) is defined as the following mathematical formula 11.
[ number 11]
i(λ，t，SET)＝C3*(1/λ)*(t+C4)*SET (11)
Wherein, C3、C4Is a constant determined by measuring the reference fluid.
Fig. 9 is a view showing a case where the measurement result of fig. 7 is corrected by range correction including only the universal range correction component and the fluid specific range correction component. As can be seen from fig. 9, the span error can be corrected regardless of the type of fluid and the flow rate.
Next, a case where the span correction amount further includes a bypass span correction component will be described.
The range error also includes a bypass range error which is affected by the flow dividing ratio and the structure of the sensor flow path SC and the bypass flow path BC. This error is considered to occur due to the following reasons: if the ambient temperature changes, the viscosity of the fluid changes, thereby changing the split ratio of the sensor flow passage SC and the bypass flow passage BC. Therefore, the function j (λ, t) of the bypass range correction component is defined by the following equation 12.
[ mathematical formula 12]
j(λ，t)＝C5*t+(C6t+C7)*(1/λ)2+C8 (12)
Wherein, C5、C6、C7、C8Is a constant determined based on measured data while flowing through a reference fluid.
Fig. 10 shows a comparative example in which the span correction amount includes only the common span component and the fluid-specific span correction component, and the span correction amount further includes the bypass span correction component. It can be seen that the span error can also be reduced regardless of the type of fluid and temperature. Further, since the measurement is performed using the thermal flow meters having different split ratios, the measurement result of the span correction of SF6 in fig. 9 (a) is different from the result of the span correction before the correction in the measurement of the span correction of SF6 in fig. 10. However, it can be seen from fig. 10 that the span error can be further reduced by adding the bypass span correction component j (λ, t).
The reason why the accuracy of correction is improved by defining the function j (λ, t) of the bypass range correction component shown in equation 12 will be described qualitatively. The reason for the change in the split ratio is expected to be that the viscosity of the fluid changes due to the change in the ambient temperature. Here, the relational expression between the viscosity and the temperature is, for example, expression 13.
[ mathematical formula 13]
Wherein, mu: viscosity ratio, m: mass of one molecule, kB: boltzmann constant, d: the diameter of the gas molecules.
On the other hand, the relationship between the thermal conductivity and the temperature is shown in mathematical formula 14.
[ number 14]
If mathematical formula 13 and mathematical formula 14 are compared, it is considered that both the viscosity ratio and the thermal conductivity are values proportional to the temperature to the power of 0.5 and the temperature dependence is very similar. Therefore, in the present embodiment, it is considered that the span correction amount for each fluid can be calculated by using the thermal conductivity instead of using the viscosity ratio, and the correction can be performed with high accuracy.
Finally, the correction calculation unit 6 calculates a corrected flow rate based on the sensor output, the zero correction amount, and the span correction amount, and outputs the calculated flow rate as a final output.
In this way, since the thermal flow meter 100 of the present embodiment calculates the flow rate based on the upstream voltage Vu, the downstream voltage Vd, and the thermal conductivity of the fluid, it is possible to accurately correct the zero point error and the span error that change under the influence of the environmental temperature and the fluid flow rate in a wide temperature range, and to output an accurate flow rate.
Further, it is not necessary to perform an experiment for determining the correction amount for each fluid in order to calculate the zero point correction amount and the span correction amount, and the correction amount can be calculated by substituting the thermal conductivity of each fluid type into a common calculation formula. Therefore, even when the types of fluids flowing in the flow path are used in a plurality of applications, it is not necessary to perform an experiment of a correction amount calculation formula dedicated for specifying the number of types of fluids, and the setting work can be reduced.
Other embodiments will be described.
In the above embodiment, both the zero point correction amount calculation unit and the span correction amount calculation unit are provided, but the zero point correction amount calculation unit or the span correction amount calculation unit of the present invention may be used alone depending on the application. For example, when only the zero point correction is performed, the flow rate calculation formula shown in equation 15 may be defined.
[ mathematical formula 15]
In addition, when the span correction amount calculation portion is used alone, the span correction amount calculation portion may include the post-correction temperature index calculation portion and the current temperature calculation portion in its configuration. In addition, as the span correction amount, the bypass span correction component may be omitted and only the universal span correction component and the fluid specific span correction component may be included.
In the embodiment, the square of the sum of the upstream voltage and the downstream voltage is used as the temperature index, but the sum of the square of the upstream voltage and the square of the downstream voltage may be used. Even in this manner, the linear characteristic with respect to the temperature can be improved over a wide temperature range, and the current temperature can be estimated with high accuracy.
The thermal conductivity of each fluid used for calculating the zero point correction amount and the span correction amount may be stored in the memory as a physical property value in advance, or the thermal conductivity may be calculated based on the upstream voltage and the downstream voltage. More specifically, since there is a predetermined relational expression between the thermal conductivity and the ratio of the amount of change in the upstream voltage and the amount of change in the downstream voltage at the time of change in the flow rate, the thermal conductivity of the fluid can be calculated from the upstream voltage and the downstream voltage based on the relational expression.
In the above embodiment, the application example of the present invention to the constant temperature driving type thermal flowmeter was described, but the present invention can also be applied to the constant current driving type thermal flowmeter. More specifically, in the case of the constant current drive method, one bridge circuit including an upstream resistance element and a downstream resistance element is provided, and control is performed so that the current side applied to each resistance element is constant. In the constant current method, a voltage difference between an upstream voltage applied to the upstream resistance element and a downstream voltage applied to the downstream resistance element is output from the bridge circuit. Thus, the thermal flowmeter of the constant temperature system of the embodiment is common to the thermal flowmeter of the constant temperature system of the embodiment in that there is only one voltage difference output from the bridge circuit, and the voltage difference is output based on the upstream voltage and the downstream voltage. Therefore, the present invention can be applied to a constant current thermal flowmeter. The present invention may be applied to a thermal flowmeter of a constant temperature difference drive system configured to maintain a predetermined temperature difference between an upstream resistance element and a downstream resistance element.
Further, the upstream voltage and the downstream voltage of the present invention are not limited to the voltage applied for heat generation. More specifically, the present invention can also be applied to a thermal type flow meter: the heating resistor provided between the upstream resistance element and the downstream resistance element is caused to generate heat, the upstream resistance element and the downstream resistance element function as temperature sensors, and the flow rate is calculated based on an upstream voltage and a downstream voltage applied in accordance with the temperature.
The present invention can be used not only for the purpose of measuring a flow rate, but also for a temperature measuring device that measures the current temperature of a flow rate to be measured. More specifically, there may be provided a temperature measuring device characterized by comprising: a flow passage through which a fluid of a measurement object flows; an upstream resistance element disposed upstream of the flow channel; a downstream resistance element disposed downstream of the flow channel; a post-correction temperature index calculation unit that calculates a post-correction temperature index based on at least a pre-correction temperature index calculated from an upstream voltage that is a voltage applied to the upstream resistance element and a downstream voltage that is a voltage applied to the downstream resistance element, and a correction constant calculated from a thermal conductivity of the fluid to be measured; and a current temperature calculation unit for calculating a current temperature based on the corrected temperature index. Further, as another embodiment of the temperature measuring apparatus, a current temperature calculating section that calculates a current temperature from the corrected temperature index may be omitted. More specifically, for example, when a value in centigrade is not required, the corrected temperature index can be used as it is as a temperature. Even in this way, the corrected temperature indicator reflects the exact temperature of the fluid and can be well applied, for example, to correction and other uses.
In the above embodiment, the influence of the zero point error due to the difference in the type and flow rate of the fluid is actually measured, and as shown in fig. 4 (c) and the like, the correction constant K is approximated by a linear expression using the thermal conductivity as a variable from the measurement data, and the correction constant K can be calculated from the thermal conductivity of each fluid. Here, the approximate expression is not limited to a linear expression, and may be approximated by another polynomial expression. The same applies to span correction.
The bypass range error correction component j (λ, t) of the above embodiment is a function of thermal conductivity and temperature, and a value related to the current flow rate may be used as a variable so that the influence of the flow rate can be corrected.
The above-described functions can be achieved by adding the configuration of the present invention to a conventional thermal flowmeter using a program storage medium storing a program for a thermal flowmeter used in the thermal flowmeter of the present invention. As the program storage medium, a CD, a DVD, an HDD, a flash memory, or the like can be used.
Various modifications and combinations of the embodiments can be made without departing from the spirit of the present invention.
Industrial applicability
When the thermal flowmeter of the present invention is used, the flow rate of the component gas or the like can be measured with high accuracy in the semiconductor manufacturing process, and the product quality or the like can be improved.

Claims (11)

1. A thermal flow meter characterized by comprising:
a flow passage through which a fluid of a measurement object flows;
an upstream resistance element disposed upstream of the flow channel;
a downstream resistance element disposed downstream of the flow channel; and
a flow rate calculation unit that calculates an ambient temperature based on an upstream voltage that is a voltage applied to the upstream resistance element, a downstream voltage that is a voltage applied to the downstream resistance element, and a thermal conductivity of the fluid to be measured, and calculates a flow rate of the fluid to be measured based on the upstream voltage, the downstream voltage, and the ambient temperature,
the flow rate calculating section calculates the flow rate of the fluid,
calculating a pre-correction temperature index according to the sum of the upstream voltage and the downstream voltage;
calculating a correction constant from the thermal conductivity of the fluid of the measurement object;
calculating a corrected temperature index according to the temperature index before correction and the correction constant;
calculating the environmental temperature according to the corrected temperature index;
and calculating the flow rate of the fluid of the measuring object according to the difference between the upstream voltage and the downstream voltage and the environment temperature.
2. A thermal flow meter is characterized in that,
a flow passage through which a fluid of a measurement object flows;
an upstream resistance element disposed upstream of the flow channel;
a downstream resistance element disposed downstream of the flow channel; and
a flow rate calculation unit that calculates a flow rate of the fluid to be measured based on an upstream voltage that is a voltage applied to the upstream resistance element, a downstream voltage that is a voltage applied to the downstream resistance element, and a thermal conductivity of the fluid to be measured,
the flow rate calculation unit includes:
a sensor output calculation unit that calculates a sensor output related to the flow rate of the fluid to be measured based on a voltage difference that is a difference between the upstream voltage and the downstream voltage;
a zero point correction amount calculation unit that calculates a zero point correction amount of the sensor output based on a thermal conductivity of the fluid to be measured; and
and a correction calculation unit that calculates a corrected flow rate based on at least the sensor output and the zero point correction amount.
3. Thermal flow meter according to claim 2,
the zero point correction amount calculation unit includes:
a zero point correction temperature function storage section that stores a zero point correction temperature function as a function of temperature, the zero point correction temperature function being determined as: a difference between the fluid to be measured and the sensor output becomes zero in a predetermined temperature range when the fluid does not flow in the flow channel;
a corrected temperature index calculation unit that calculates a corrected temperature index based on at least a temperature index before correction calculated from the upstream voltage and the downstream voltage and a correction constant calculated from a thermal conductivity of the fluid to be measured;
a current temperature calculation unit for calculating a current temperature based on the corrected temperature index; and
and a zero point correction amount determining unit that determines a zero point correction amount based on the zero point correction temperature function and the current temperature.
4. The thermal flow meter according to claim 3, wherein the correction constant is a value calculated based on the square of the inverse of the thermal conductivity.
5. The thermal flow meter according to claim 3, wherein the corrected temperature index calculation unit calculates the corrected temperature index based on the pre-correction temperature index, the correction constant, and the sensor output.
6. Thermal flow meter according to claim 2,
the flow rate calculation unit further includes a span correction amount calculation unit that calculates a span correction amount output by the sensor based on a thermal conductivity of the fluid to be measured,
the correction calculation unit calculates a corrected flow rate based on at least the sensor output and the span correction amount.
7. The thermal flow meter of claim 6, wherein the span correction comprises: a universal range correction component that changes only depending on temperature; and a fluid-inherent range correction component that changes depending on at least the thermal conductivity of the fluid to be measured.
8. The thermal flow meter of claim 7, wherein said fluid natural range correction component is a function of said thermal conductivity, said sensor output and temperature as variables.
9. The thermal flow meter according to claim 7,
the flow path includes:
a bypass flow passage through which the fluid of the measurement object flows, the bypass flow passage being provided with a fluid resistance element; and
a sensor flow path provided in such a manner as to connect the front and rear of the fluid resistance element with respect to the bypass flow path, the upstream resistance element and the downstream resistance element being provided on the outer sides,
the span correction amount further includes a bypass span correction component for performing correction corresponding to the bypass flow path, and the bypass span correction component is a function having at least a thermal conductivity of the fluid to be measured as a variable.
10. A temperature measuring device characterized by comprising:
a flow passage through which a fluid of a measurement object flows;
an upstream resistance element disposed upstream of the flow channel;
a downstream resistance element disposed downstream of the flow channel;
a post-correction temperature index calculation unit that calculates a post-correction temperature index based on at least a pre-correction temperature index calculated from an upstream voltage that is a voltage applied to the upstream resistance element and a downstream voltage that is a voltage applied to the downstream resistance element, and a correction constant calculated from a thermal conductivity of the fluid to be measured; and
and a current temperature calculation unit for calculating a current temperature based on the corrected temperature index.
11. A thermal flow calculation method for a thermal flow meter, the thermal flow meter comprising: a flow passage through which a fluid of a measurement object flows; an upstream resistance element disposed upstream of the flow channel; and a downstream resistive element disposed downstream of the flow channel,
the thermal flow rate calculation method is characterized by including:
an ambient temperature calculation step of causing a computer to function as a flow rate calculation unit that calculates an ambient temperature based on an upstream voltage that is applied to the upstream resistance element, a downstream voltage that is applied to the downstream resistance element, and a thermal conductivity of the fluid to be measured,
a fluid flow rate calculation step of calculating a flow rate of the fluid of the measurement object based on the upstream voltage, the downstream voltage, and the ambient temperature,
in the fluid flow rate calculating step,
calculating a pre-correction temperature index according to the sum of the upstream voltage and the downstream voltage;
calculating a correction constant from the thermal conductivity of the fluid of the measurement object;
calculating a corrected temperature index according to the temperature index before correction and the correction constant;
calculating the environmental temperature according to the corrected temperature index;
and calculating the flow rate of the fluid of the measuring object according to the difference between the upstream voltage and the downstream voltage and the environment temperature.
CN201480031064.6A 2013-09-09 2014-09-08 Thermal flowmeter, temperature measuring device, and thermal flow rate calculating method Active CN105264341B (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP2013185885 2013-09-09
JP2013-185885 2013-09-09
PCT/JP2014/073633 WO2015034081A1 (en) 2013-09-09 2014-09-08 Thermal flow meter, temperature measurement device, and thermal flow meter program

Publications (2)

Publication Number Publication Date
CN105264341A CN105264341A (en) 2016-01-20
CN105264341B true CN105264341B (en) 2019-12-31

Family

ID=52628538

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201480031064.6A Active CN105264341B (en) 2013-09-09 2014-09-08 Thermal flowmeter, temperature measuring device, and thermal flow rate calculating method

Country Status (5)

Country Link
US (1) US10337900B2 (en)
JP (1) JP6433074B2 (en)
KR (1) KR102266217B1 (en)
CN (1) CN105264341B (en)
WO (1) WO2015034081A1 (en)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP4122515A1 (en) * 2016-09-16 2023-01-25 Fisher & Paykel Healthcare Limited Thermistor flow sensor having multiple temperature points
WO2018142456A1 (en) * 2017-01-31 2018-08-09 東京電力ホールディングス株式会社 Relationship information setting method, flow velocity determination method, relationship information setting system, and flow velocity determination system and program
EP3421947B1 (en) * 2017-06-30 2019-08-07 Sensirion AG Operation method for flow sensor device
JP2019020291A (en) * 2017-07-19 2019-02-07 アズビル株式会社 Heat flowmeter and flow rate correction method
US10852235B2 (en) * 2018-03-02 2020-12-01 Ecolab Usa Inc. Ultralow range fluorometer calibration
EP3614109A1 (en) * 2018-08-22 2020-02-26 Technische Universität Graz Measuring device and measuring probe for a flowing fluid
CN114935388B (en) * 2022-07-26 2022-11-01 成都千嘉科技股份有限公司 Correction method implemented by correction system based on ultrasonic gas meter

Family Cites Families (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0663803B2 (en) * 1989-08-07 1994-08-22 山武ハネウエル株式会社 Zero compensation method
JP2875919B2 (en) 1991-11-20 1999-03-31 シーケーディ株式会社 Mass flow meter
JPH0989619A (en) * 1995-07-19 1997-04-04 Ricoh Co Ltd Heat-sensitive flowmeter
JP2001165731A (en) 1999-09-30 2001-06-22 Yazaki Corp Flow sensor and flowmeter using the same
JP3726261B2 (en) * 2001-09-28 2005-12-14 株式会社山武 Thermal flow meter
JP3914116B2 (en) * 2002-08-28 2007-05-16 株式会社山武 Thermal flow meter
US7043374B2 (en) * 2003-03-26 2006-05-09 Celerity, Inc. Flow sensor signal conversion
US7467027B2 (en) * 2006-01-26 2008-12-16 Mks Instruments, Inc. Compensation for thermal siphoning in mass flow controllers
US7971480B2 (en) * 2008-10-13 2011-07-05 Hitachi Metals, Ltd. Mass flow controller having a first pair of thermal sensing elements opposing a second pair of thermal sensing elements
JP5629212B2 (en) * 2009-09-30 2014-11-19 株式会社堀場エステック Flow sensor
JP5969760B2 (en) * 2011-12-27 2016-08-17 株式会社堀場エステック Thermal flow sensor
JP5558599B1 (en) * 2013-02-13 2014-07-23 三菱電機株式会社 Thermal air flow meter
WO2015029890A1 (en) * 2013-08-28 2015-03-05 株式会社堀場エステック Fluid analysis device, thermal flowmeter, mass flow controller, fluid property specification device, and program for fluid analysis device

Also Published As

Publication number Publication date
KR102266217B1 (en) 2021-06-18
KR20160053844A (en) 2016-05-13
WO2015034081A1 (en) 2015-03-12
US20160131512A1 (en) 2016-05-12
US10337900B2 (en) 2019-07-02
CN105264341A (en) 2016-01-20
JP6433074B2 (en) 2018-12-05
JPWO2015034081A1 (en) 2017-03-02

Similar Documents

Publication Publication Date Title
CN105264341B (en) Thermal flowmeter, temperature measuring device, and thermal flow rate calculating method
US10024700B2 (en) Fluid analysis device
CN101762299B (en) Mass flow meter and mass flow controller
KR101717069B1 (en) Mass flow controller with enhanced operating range
US10514289B2 (en) Mass flow rate measurement method, thermal mass flow meter using said method, and thermal mass flow controller using said thermal mass flow meter
US8504311B2 (en) Method and mass flow controller for enhanced operating range
JP4944037B2 (en) Reynolds number correction function for mass flow sensors
US7363182B2 (en) System and method for mass flow detection device calibration
JP5629212B2 (en) Flow sensor
US8874387B2 (en) Air flow measurement device and air flow correction method
EP1431717A1 (en) Flow rate measuring instrument
CN112179432A (en) Flow sensor, correction device and correction method for flow sensor, flow control device, and storage medium
CN117099064A (en) Mass flow controller utilizing nonlinear component function
WO2022004001A1 (en) Thermal flow meter, flow rate control device, thermal flow rate measurement method, and program for thermal flow meter
CN116907609A (en) Temperature compensation method of constant temperature difference type thermal gas flowmeter and electronic equipment

Legal Events

Date Code Title Description
C06 Publication
PB01 Publication
C10 Entry into substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant